14
In round ducts, take velocity readings at the center of equal concentric
areas; take at least 20 readings along two diameters. In square or
rectangular ducts, take a minimum of 16 and a maximum of 64 readings
at centers of equal areas. Calculate the average of all readings.
For maximum accuracy, observe the following precautions:
1. Perform the traverse in a section of the duct where the air stream is
as uniform as practical. This is generally a location of eight or more
duct diameters of straight duct upstream from the traverse location.
2. Do not take the traverse near a duct elbow, transition or obstruction.
3. Make a complete, careful and accurate traverse and record the
results on a worksheet.
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